Mac
While you can install the free MediaTomb, it's quite complex--steer clear if you're not familiar with OSX command line. There's also the paid-for TwonkyMedia, but we ran into a number of problems and poor PS3 compatibility. Not to mention a non-native OSX interface.The best option for your Mac is MediaLink for the PS3, and Connect360 for 360, both downloadable from Nullriver for US$20 each.
After downloading and installing, you'll need to double click on the .prefPane files included. Choose whether to install for a single user or all users to add the servers to your System Preferences panel.
For Connect360, load the app from the System Preferences panel (found under Applications folder), make sure your 360 is on and click Start. It will automatically access your iTunes and iPhoto libraries, but you'll need to point it to where your movies are. Click settings, select the Movies icon and change the drop down box to "Other" to select the folder you want.
MediaLink is similar, but you can add multiple media folders to it by selecting the Folders option and clicking the plus button.
Return to your 360 Media blade, or PS3 media sections and you should be able to contact your Mac.
